MAGNETIC FIELD

 

What does the magnetic field mean?

Definition: A magnetic field is a force field created as a result of the movement of electric charges (flow of electricity). The strength (intensity or current) of a magnetic field is measured in Gauss (G) or Tesla (T). The flux decreases with the distance to the source that causes the field.

How does a magnetic field work?

Magnetism is a physical phenomenon by which objects exert forces of attraction or repulsion on other materials. The only known natural magnet is a mineral called magnetite, however, all materials are influenced, to a greater or lesser extent, by the presence of a magnetic field.

HOMEMADE COMPASS

Our planet acts like a giant magnet, creating a magnetic field that shields Earth from radiation from space.

Magnetized metals naturally align with that field, and one can take advantage of that invisible effect in the experiment that shows us how to magnetize a needle to create a compass.

What we need?

1. A sewing needle
2. A cork or plastic cap from a bottle
3. A bar magnet
4. A shallow bowl of water

How it's done?

Instructions for making a compass:

1. Cut a circle of cork about 5mm to 10mm thick. You can also use a plastic bottle cap.

2. Rub the needle about 50 times with the north side of the magnet. If the magnet doesn't have north marked, choose one side and use only that. Separate the magnet from the needle after each rub to reduce the chance of it becoming demagnetized. Rubbing from the hole to the tip causes the iron atoms in the needle to line up, temporarily turning it into a magnet.

3. Stick the magnetized needle on the cork and carefully put it in the dish with water.

4. The water provides a nearly frictionless surface that allows the cork to rotate until the north pole of the needle (the hole) points toward the north magnetic pole (as seen on a purchased compass). If the needle is rubbed with the magnet in the other direction, it will be the tip that points north.

Do not put the coil near computers or other devices that contain magnets as they may affect the field lines. The needle will lose its magnetic charge over time.

Why is it magnetized?

Iron, nickel, and cobalt contain small regions called magnetic domains, in which electrons line up in the same direction. These domains point in different directions, so they tend to cancel each other out.

When one of those metals is exposed to a strong magnetic field, the domains align, making it a temporary magnet.

Why does the compass point north?

Once the needle is magnetized, it naturally aligns with the Earth's strongest magnetic field.

Scientists believe that this field, called the magnetosphere, is created by electrical currents generated by the churning of the molten iron core deep within the planet.

This means that the Earth acts as if it had a magnet passing through it, with the south pole of the magnet located near the geographic north of the planet. Since opposites attract, the north pole of a magnetized needle points in that direction.